Originally Posted by tandempower

The main issue is minimizing motor-traffic or at least keeping it a small-enough proportion of total traffic that it doesn't become the defining transportation paradigm in planning and development. I hate to put such a negative focus on driving but until motor-traffic is @50% of total traffic or less, I don't think city planning and development will be truly bike- and transit- friendly.

Once @50% or more of total traffic is non-motorized and transit, and sprawl development is a thing of the past, I don't see why cities can't expand indefinitely. After all, 'urban' at that point is essentially replaced with 'forest in-fill development that minimizes motor traffic and eliminates its presence altogether wherever possible.' In such a situation, why would new suburban development add to traffic problems in existing parts of the city? The problem with sprawl is that it snow-balls motor-traffic as it grows.